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Discussion Starter #1
i have a freebie carb from an 98 yamaha rt100.
its supposed to be a 22mm

how do you find out how big of a bore a carb has?
how do you know what size carb body you need to order parts for?
throttle springs, what size (diameter) throttle slide etc.
sudco has a diagram for vm18, vm29, vm33 but no 22mm. i am assuming it shares most of the body except an altered bore.

are freebie carbs worth gathering and hording?

and its for a two stroke, what should you change to make it fit a four stroke if i had a four stroke to put it on?
 

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Carbs are usually measured at the thinnest area (usually at the slide). Sudco has a bunch of different jets (air, fuel,needles,etc) and the best way to get what you need is to remove and measure your existing jet and compare it to what they offer. The Sudco catalog has the measurement of the jets in it. The Mikuni jets usually have a prefix to denote its use.
Changing a 2 stroke carb for use in a 4 stroke can get expensive as many times you will need to change the slide, emulsion tube,needle and some/all jets to get it to work correctly. Its not impossible, but usually easier to get a new, correct carb for the application.
A free carb is a free carb, and no one can have too many extra parts. Even if you eventually throw it away, it still didn't cost you anything.
DG
 

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Corey,
If it's an OEM carb chances are the standard VM parts may not fit. Jets/needles/etc. yes. Slides, and large parts...good chance no.

The same size float chambers usually serviced numerous size throat diameters, no indicator true size. If it has a choke plate...look inside the carb inlet and see if there is a number stamped inside a round circle. Keihin does this on a lot of OEM carbs, not sure about Mukuni.

If it's a round throat carb...just measure the narrow area just before the slide on the inlet side. You can usually see where this area of the body is bored out to the actual throat diameter.
JohnnyB
 
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